Contender (PSX)

Two Player Mode Main Event Characters:
Start a new boxer in the Main Event. Pick one of the boxers and imediately
save him to your memory card. Exit, then repeat with another character. When you have saved each boxer start a two-player match. At the character select screen press SQUARE to pick one of the other boxers from your memory card.

Get Jackel, Goober, Rascal and Beastman:
Go to Main Event and save any player on a memory card. Now go into
Exhibition and load the player by pressing Square. After highlighting
the player press Square again and Jackel should appear in your 2nd
Mystery box. Win the World Championship and save the game then go to
exhibition mode character select screen and press Square and Square
again to get other characters

Get up Quickly:
Rotate the D-Pad and press any other button quickly to get up fast
after a knockdown

Boxing Trainer (2 player mode):
At the 2 player mode character select screen press Square then press
Square again to select the trainer

4 New Fighters:
If you beat the Main Event by being Champ of the World. Save it then
load it back on when you get to exhibition. You get the guys were the
question marks are.

Newspaper Photo Trick (Analog Controller Only):
To get a photo of your choice in the newspaper at the end of the bout
press L3 or R3 on the ANALOG controller